The present invention relates to a flare housing. The invention is directed to an improved interior structure which facilitates the manufacturing of the flare as well as improving the reliability and performance of the flare.
Aerial flares are used for such as illumination, signaling, marking, decoys, military countermeasures and the like. A flare is typically described as a pyrotechnic device designed to produce a luminous display or illumination. Due to the nature of uses, aerial flares require a high degree of reliability in their performance. When the flare is ignited for either decoy or illumination, it is imperative that it perform, or burn as designed, or its objective will not be realized.
In the area of countermeasures, flares are now designed to defeat the most sophisticated heat-seeking missiles. Unlike earlier versions of decoy flares which were dropped from aircraft like “hot bricks”, these new infrared flare countermeasure devices are self propelled kinematic flares. Current flare housings are usually a cylindrical can, open at one end. Current kinematic flare housings are typically of a composite construction made from a reinforced resin material that is manufactured by forming resin impregnated reinforcing material over a die core, placing the formed material/die core into a mold, and applying heat/pressure to form and cure the material thereby creating the housing. The formed and cured housing is removed from its mold and the die core removed rendering the housing ready for the next steps in the flare production.
The decoy flare is built-up inside of the walls of the formed housing, first including a nose weight at the head, or closed end of the housing. The nose weight is fixed securely into position, to prevent it from coming loose and interrupting the flight-path of the flare. In certain designs, the nose weight is bonded and cured to the inside surfaces of the closed end of the flare housing with an adhesive. This is a time consuming and imprecise process due to the challenges associated with applying adhesive on the interior wall at the forward end of a formed housing with a generally small interior. For example, the dimensions of the aft end opening of one such housing is about 1.5 inches by 2 inches and the housing is about 8 inches in length. The propellant is blended and then cast into the formed housing. A propellant shaping mandrel having certain longitudinal grooves for receiving propellant is plunged into the cast propellant forcing it up around the shaping mandrel and into the longitudinal grooves. The mandrel is then fixtured in place and the propellant is then cured. Once the solid propellant is cured, the shaping mandrel is removed from the assembly. Located in the cast propellant are specific cross-sectional voids created by the propellant shaping mandrel.
The cast propellant is the energetic or pyrotechnic material creating the required thrust upon ignition. Upon ignition, the exposed surface of the propellant burns. The burn rate/pressure profile can be controlled by limiting the area of the surface that is exposed. During construction of the flare, after the propellant is added to the housing and allowed to cure, a layer of non-flammable material such as an epoxy or similar material, is applied to a portion of the exposed surfaces of the propellant and allowed to cure. The propellant surfaces coated with the non-flammable material are thus inhibited from burning and the desired control of the burn/pressure profile is achieved. For example, a layer of non-flammable material may be thickly painted on the side edges or some portion of the side edges of the propellant or extruded from a nozzle in a thick bead of material alongside the propellant analogous to laying a bead from a calking nozzle. In the prior art, this non-flammable coating is applied, essentially blindly along the propellant grain. Likewise in the prior art, the nose weight is secured in position to the closed end of the housing with an adhesive which is painted on or applied in a bead. Given the manual application of the non-flammable coating, and the necessity of applying the coating on the exposed propellant surface after the propellant is bonded to the interior of the housing, the placement is time consuming and not always precise.
To complete the construction of the flare, a threaded stud is affixed approximately in the center of the nose weight such that it protrudes into the interior of the housing for receiving and holding in place the flare grain. The flare grain is inserted into the void in the housing created by the propellant shaping mandrel and is axially aligned with the housing. The propellant is intermediate the housing and flare grain. A nozzle is affixed to the aft end of the housing for propulsion of the countermeasure flare.
The present invention facilitates the manufacture of the countermeasure, as well as providing more precise way to inhibit the burn rate/pressure profile exhibited by the flare and ensuring accurate placement of the nose weight and other internal features of the decoy.